Syringe injection systems have been in use in medical procedures for many years. Many such syringes are operated manually by advancing a plunger extension in operative connection with an internal plunger to pressurize the fluid within the syringe. In numerous medical injection procedures, however, accurate control and/or high pressures are required that cannot be achieved via manual syringe operation. A number of syringes and powered injectors for use therewith have, therefore, been developed for use in medical procedures such as angiography, computer tomography and NMR/MRI. For example, U.S. Pat. No. 5,383,858 discloses a front-loading syringe and powered injector in both pressure jacket and jacketless embodiments.
Like syringes operated manually, syringes for use with powered injectors comprise a plunger for forcing the fluid injection medium from the syringe to be injected into the patient. These plungers generally include a cooperating attachment member to enable attachment of the plunger to a powered drive member in the injector. In all cases, there is only one axial position of the injector drive member corresponding to a specific axial position of the plunger at which attachment of the drive member to the plunger is possible. Typically, the plunger must be placed in a single predetermined axial position within the syringe to enable attachment of the plunger to the injector drive member. Often, the predetermined axial position of the plunger is the rearwardmost position.
Such designs present a number of problems. For example, the attachment of the plunger to the drive member is often mechanically difficult for the user, requiring an accurate one-to-one axial alignment. Furthermore, it is preferable to be able to attach the plunger to the drive member when the plunger is not at its rearwardmost position. Attachment of the plunger to the drive member at a somewhat forward position of the plunger, for example, enables the user to draw the plunger back to check for air in the system or to check for blood in the system to ensure proper insertion of an injection needle.
A number of medical procedures also require that the injection media undergo some preparation before powered injection. In some procedures, for example, a contrast medium is received by the end user in the form of a dry powder that must be mixed with a liquid vehicle before injection. In general, the amount of liquid added to a specified amount of dry powder must be relatively precisely measured. Typically, a hand-held or manually operated syringe is used to draw the prescribed amount of liquid out of a container. This amount of liquid is then injected into a vial containing the specified amount of the powder. The liquid and powder are then mixed or agitated before injection into a patient.
For a number of reasons, it is very difficult to inject such a prepared injection medium using current powered injectors. For example, most manually operated syringes, which are typically used to draw the prepared injection medium, cannot be mounted on current powered injectors. Moreover, it is difficult to transfer the medium from a manual syringe into a syringe suitable to be mounted on currently available power injectors. Although a small number of syringes and injectors for use therewith have been developed in which the syringe can be used in a manual mode and in a powered injection mode, for example the syringe/injector system described in WO 82/1988 entitled "Mechanism For Screw Drive And Syringe Plunger Engagement/Disengagement", such syringe/injector systems suffer from the same axial alignment problems discussed above. Further, these prior art syringe/injector systems require the manual alignment of the injector drive mechanism with the syringe plunger.
It is, therefore, desirable to develop a syringe and a powered injector for use therewith which minimize or eliminate the alignment difficulties discussed above. It is also desirable to develop such a syringe and injector in which the syringe can be operated in a manual mode and in a powered injection mode.